This invention relates to coated films, sheets or foils and, more particularly, to the application of a gas-barrier coating thereto.
Lindlof, U.S. Pat. No. 3,607,365, discloses a vaporphase technique for the preparation of coatings of polyurethanes and polyureas by the reaction of isocyanates with alcohols or amines. A wide variety of substrates are disclosed including biaxially oriented polyethylene terephthalate (PET) film. The purpose of the coating is variously described as being protective and to give the coated film anti-static and anti-blocking properties. Lindlof's method involves alternately exposing a substrate to vapors of the isocyanate and then to the amine or alcohol until a polymeric coating is built up. Lindlof stresses that his reaction takes place on the substrate surface by first one compound being absorbed or reacted thereon and then the next compound reacting with the ends of the molecules of the first compound which bristles perpendicularly from the substrate surface. Neither reaction liberates any reaction by-product.
Blais et al., U.S. Pat. No. 3,829,324, discloses providing coatings of condensation polymers on polymeric substrates after electrical discharge treatment of the surface. When more than one monomeric precursor is involved, the substrate is exposed to successive exposures to the precursors. The precursors may be applied in the solid, liquid or vapor state.
Hoheisel, U.S. Pat. No. 3,843,481, discloses improving the heat and/or flame resistance of polyester films by applying a covering layer of an aromatic polyamide, polyamide-imide or polyimide. The covering layer is applied over an intermediate layer of the reaction product of an aromatic polyisocyanate with an epoxide resin. The covering layer can be applied from solvents, dispersions or by extrusion coatings. The products are said to be particularly suitable for use in electrical insulations.